Small stream fish ladder

ABSTRACT

A fish ladder for small-bodied fishes that is easily portable so as to enable installation and use in a given water course when needed, and relocation at other times. The fish ladder defines a channel with generally evenly spaced baffles in the channel disposed at about 45° angles to the channel bottom. The ladder includes a bracket that enables the ladder to be attached to any size, shape, and material of culvert or other drainage structure. The ladder is attached to the bracket with a hinge mechanism, so as to accommodate virtually any height of drop presented by small drainage structures. With extendable legs, a fish ladder according to embodiments of the invention is able to be installed in streams up to 6 feet deep. The ladder can be scaled so as to target passage of small-bodied non-game species such as minnows, while also passing larger game species as well.

FIELD OF THE INVENTION

The present invention relates to fisheries management tools, and more specifically to fish ladders.

BACKGROUND OF THE INVENTION

Obstructions to natural water flow, caused for example by roads, can fragment aquatic ecosystems and thereby affect fish populations. Typically, culverts are installed under road grades to facilitate passage of water, but such culverts often form waterfalls at the drainage end due to the change in elevation, and hence may themselves form a barrier to fish passage upstream. Such culvert road crossings can occur at least once every square mile in the Great Plains.

Fish typically must move upstream during short periods of the year for purposes of spawning. The obstacle to fish passage presented by culverts can be a particular problem for small bodied fishes, such as minnows, suckers, and darters, as they are unable to navigate even the small waterfalls and current presented by culvert outflows.

Fish ladders to assist fish in moving upstream in water courses are known. For example, in the Pacific Northwest of the U.S., fish ladders and fishways have long been deployed to enable salmon to migrate around the large hydroelectric dams that have been built in the major rivers in that area.

Different types of fish ladders have been developed in the past. The pool-and-weir fishway is one of the oldest designs and is typically used at large barriers. These structures present a set of steps, with pools before each step. A drawback of pool-and-weir designs, however, is that they are most suited to large-bodied fishes having significant jumping ability and are much less effective in promoting movement of small-bodies fishes and fish species.

“Denil” type fish ladders incorporate a ramp approach with roughing features to simulate natural rapids. Baffles catch water and turn it back on itself to create areas of low velocity, enabling fish to ascend the ladder against the current. Denil type fish ladders are generally more effective in promoting movement of small-bodied fishes. A drawback of Denil type and other prior fish ladder designs, however, is that they are typically permanent structures. Placing permanent fish ladders or fishways at every location where they would be desirable to promote optimal fish management is prohibitively expensive, and also wasteful, in that the ladders are only needed for a short period of time to enable migration of fish, and otherwise are unnecessary. Further, these structures can take weeks or months to plan and install. Still further, such permanent structures can cause unintended and undesirable alterations to the water course, such as silting, or scour patterns in the downstream pool.

What is needed is an effective fish ladder structure for small-bodied fishes that is easily portable so as to enable installation and use in a given water course when needed, and relocation at other times.

SUMMARY OF THE INVENTION

Embodiments of the present invention address the need for an effective fish ladder structure for small-bodied fishes that is easily portable so as to enable installation and use in a given water course when needed, and relocation at other times. According to embodiments, a fish ladder defines a channel with generally evenly spaced baffles in the channel disposed at about 45° angles to the channel bottom. The ladder includes a bracket that enables the ladder to be attached to any size, shape, and material of culvert or other drainage structure. The ladder can be attached to the bracket with a hinge mechanism, so as to accommodate virtually any height of drop presented by small drainage structures. With extendable legs, a fish ladder according to embodiments of the invention is able to be installed in streams up to 6 feet deep. The ladder can be scaled so as to target passage of small-bodied non-game species such as minnows, while also passing larger game species as well.

Embodiments of the present invention provide a fish ladder that is modular, relatively small, able to be transported with a light truck, and installed by one or two people in 1 to 4 hours. Fisheries managers can easily install the ladder to target a species of fish when they are migrating, and then move the ladder to target other species in other areas during different times in the year. With a funnel trap on the outlet of the ladder, it can be used as a research tool as well. Taking little effort or resources to install, along with the ability to attach to all material, size, and shapes of drainage structures, embodiments of the invention give fisheries managers a tool to improve stream connectivity without the cost and effort associated with traditional fish ladders or with replacing existing drainage structures.

According to an embodiment, a fish ladder includes a structure interface adapted to attach to a drainage structure, the structure interface portion including a weir plate, and a ladder defining a channel for conveying water in a flow direction, the ladder including a plurality of baffles disposed across the channel generally transverse to the flow direction, the ladder operably coupled to the interface structure with a detachable hinged connection. The detachable hinged connection can include at least one hinge pin receiver on the structure interface, the at least one hinge pin receiver defining a first bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a second bore, and a hinge pin received through the first bore and the second bore. The ladder is shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface. The channel can be defined by a pair of spaced apart substantially parallel side panels and a bottom panel extending between the side panels.

In embodiments, the baffles are angled rearwardly toward the structure interface, and may be angled at about 45 degrees relative to a bottom of the channel. In embodiments, the ladder can include at least one support leg adapted to attach to the ladder. The length of the support leg may be adjustable.

In an embodiment, a system for enabling fish migration includes a drainage structure, and a fish ladder operably couplable to the drainage structure. The fish ladder includes a structure interface with a weir plate adapted to attach to the drainage structure, and a ladder defining a channel for conveying water in a flow direction. The ladder includes a plurality of baffles disposed across the channel generally transverse to the flow direction. The ladder is operably coupled to the interface structure with a detachable hinged connection. In an embodiment, the detachable hinged connection can include at least one hinge pin receiver on the structure interface, the at least one hinge pin receiver defining a first bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a second bore, and a hinge pin received through the first bore and the second bore. The ladder may be shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface.

In embodiments, the channel may be defined by a pair of spaced apart substantially parallel side panels and a bottom panel extending between the side panels. The baffles may be angled rearwardly toward the structure interface at about 45 degrees relative to a bottom of the channel.

In embodiments, the system can include at least one support leg adapted to attach to the ladder. A length of the support leg may be adjustable.

In an embodiment, a fish ladder can include a structure interface adapted to attach to a drainage structure, the structure interface portion including a weir plate presenting a top flange and a locating structure extending upwardly from the top flange. The fish ladder further includes a ladder with a pair of spaced apart side plates and a bottom plate defining a channel for conveying water in a flow direction, the ladder including a plurality of generally planar baffles extending between the side plates generally transverse to the flow direction, the baffles being disposed such that the plane of the baffles is angled relative to the bottom plate and a top edge of each baffle is disposed closer to the structure interface than a bottom edge of the baffle. The ladder is operably coupled to the interface structure with a detachable hinged connection. The baffles may be angled at about 45 degrees relative to the bottom plate.

In an embodiment, the detachable hinged connection includes a pair of spaced apart hinge pin receivers on the structure interface, each hinge pin receiver defining a bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a bore, and a hinge pin received through the bores of the hinge pin receivers and the bore of the pin receiving sleeve. The ladder can be shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:

FIG. 1 depicts a fish ladder according to an embodiment of the invention attached to a culvert and in use;

FIG. 2 is an isometric view of the fish ladder depicted in FIG. 1;

FIG. 3 is a top view of the fish ladder of FIG. 2;

FIG. 4 is a cross-sectional view of the fish ladder of FIG. 2 taken at section 4-4 of FIG. 3;

FIG. 5 is a side elevation view of the fish ladder of FIG. 2 with the ladder in a horizontal position;

FIG. 6 is a front elevation view of the fish ladder of FIG. 2 with the ladder positioned in a downwardly sloped orientation;

FIG. 7 is an isometric view of the drainage structure interface portion of the fish ladder of FIG. 2;

FIG. 8 is an isometric view of the ladder portion of the fish ladder of FIG. 2;

FIG. 9 is a side elevation view of the fish ladder of FIG. 2 with an extendable leg attached to the lower end of the ladder;

FIG. 10 is an elevation view of the drainage structure interface portion of a fish ladder according to an embodiment of the invention attached to a culvert;

FIG. 11 is a top plan view of the drainage structure interface portion of a fish ladder according to an embodiment of the invention attached to a culvert;

FIG. 12 is a side isometric view of the fish ladder of FIG. 1 during installation; and

FIG. 13 depicts an isometric view of the fish ladder of FIG. 1 with a funnel trap attached according to an embodiment of the invention.

While the present invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the present invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

There is depicted in FIGS. 1-13 a small stream fish ladder 20 according to an embodiment of the invention. Fish ladder 20 generally includes drainage structure interface 22 and ladder 24. Drainage structure interface 22 generally includes weir plate 26, top flange 28, locating structure 30, and hinge pin receivers 32, 34. Locating structure 30 projects upwardly from top flange 28 and includes side members 36, 38, and top member 40. Hinge pin receivers 32, 34, are spaced apart on top flange 28 along front edge 42, and each define a bore 44.

Ladder 24 generally includes spaced apart side panels 46, 48, bottom panel 50, baffles 52, pin receiving sleeve 54, and hinge pin 56. Side panels 46, 48, are disposed parallel to each other, and with bottom panel 50, define channel 58. Baffles 52 extend between side panels 46, 48, and are disposed at about a 45 degree angle relative to bottom panel 50, with the top edge 60 of each baffle 52 angled toward proximal end 62 of ladder 24, and against the direction of water flow WF as depicted in FIG. 4. Each side panel 46, 48, is generally trapezoidal with angled distal end 64. Proximal end 62 defines notch 66, with angled portion 68 extending from notch 66 to bottom edge 70. Pin receiving sleeve 54 defines bore 71, and is disposed at corner 72 of notch 66 and extends between side panels 46, 48.

As depicted in FIGS. 1 and 10-12, ladder 20 is installed at the drainage end of a culvert 74 by first attaching drainage structure interface 22 so that weir plate 26 extends across the bottom edge of culvert 74, forming a dam. Angle brackets 76 may be used to attach weir plate 26 with lag bolts 78 screwed into culvert 74, and bolts 80 through weir plate 26. It will be readily appreciated that structure interface may be attached to culvert 74 by any other suitable method including locking mechanisms, latches, or other mechanical fasteners. In addition, although culvert 74 is depicted herein as a cylindrical corrugated steel structure, culvert 74 may be any other structure such as is commonly used for providing drainage, for example, a concrete box culvert.

With structure interface 22 in place as depicted in FIG. 10, water will be impounded behind weir plate 26, and will eventually overtop top flange 28 as depicted in FIG. 1. Ladder 24 is attached to structure interface 22 by registering bore 71 of pin receiving sleeve 54 with bores 44 of hinge pin receivers 32, 34, positioning side panel ends 82, 84, abutting the outer surfaces of side members 36, 38, respectively, of locating structure 30, and inserting hinge pin 56 through bores 44 and bore 71 as depicted in FIG. 12. From the horizontal position as depicted in FIG. 12, ladder 24 can then be pivoted about hinge pin 56 until lower edge 86 of bottom plate 50 rests on the bottom of the water course as depicted in FIG. 1, or until angled portion 68 abuts weir plate 26 as depicting in FIG. 9. If lower edge 86 is still above the water course bottom 88, one or more leg assemblies 90 can be attached to ladder 24 for support as depicted in FIG. 9. Leg assemblies 90 may include ladder interface 92, shaft portion 94, and bottom plate 96. It will be appreciated that shaft portion 94 may be telescoping so as to enable different lengths for leg assembly 90, and ladder interface 92 may be a suitable mechanism so as to enable easy attachment and detachment of shaft portion 94 from ladder interface 92. With ladder 24 angled downwardly from structure interface 22, water overtopping top flange 28 will flow down ladder 24, with areas of low velocity in pockets 98 between baffles 52, enabling fish to ascend ladder 24 against the direction of water flow WF.

It will be appreciated that fish ladder 20 may be made with any desired dimensions while remaining within the scope of the invention. In a particular embodiment, ladder 24 may be made with a length L of about 80 inches, a width W of about 18 inches, a depth D of about 14½ inches, a baffle height D1 of about 7.8 inches, and a baffle spacing of about 5¾ inches. These dimensions are effective for promoting fish management, and also enable the ladder 20 to fit easily into the bed of a light truck for transportation.

FIG. 13 depicts a fish ladder according to embodiments of the invention with funnel trap 100 coupled to locating loop 30. Funnel trap 100 may be any such structure as generally known in the art, and includes wire mesh sides 102, 104, 106, 108, wire mesh end 110, and wire mesh funnel 112 with loop 114 defining opening 116. Fish exiting from ladder 24 will exit through opening 116, and will become trapped in funnel trap 100, thereby enabling their numbers to be counted for research purposes.

The foregoing descriptions present numerous specific details that provide a thorough understanding of various embodiments of the invention. It will be apparent to one skilled in the art that various embodiments, having been disclosed herein, may be practiced without some or all of these specific details. In other instances, components as are known to those of ordinary skill in the art have not been described in detail herein in order to avoid unnecessarily obscuring the present invention. It is to be understood that even though numerous characteristics and advantages of various embodiments are set forth in the foregoing description, together with details of the structure and function of various embodiments, this disclosure is illustrative only. Other embodiments may be constructed that nevertheless employ the principles and spirit of the present invention. Accordingly, this application is intended to cover any adaptations or variations of the invention.

For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of 35 U.S.C. §112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim. 

What is claimed is:
 1. A fish ladder comprising: a structure interface adapted to attach to a drainage structure, the structure interface portion including a weir plate; and a ladder defining a channel for conveying water in a flow direction, the ladder including a plurality of baffles disposed across the channel generally transverse to the flow direction, the ladder operably coupled to the interface structure with a detachable hinged connection.
 2. The fish ladder of claim 1, wherein the detachable hinged connection comprises at least one hinge pin receiver on the structure interface, the at least one hinge pin receiver defining a first bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a second bore, and a hinge pin received through the first bore and the second bore.
 3. The fish ladder of claim 2, wherein the ladder is shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface.
 4. The fish ladder of claim 1, wherein the channel is defined by a pair of spaced apart substantially parallel side panels and a bottom panel extending between the side panels.
 5. The fish ladder of claim 1, wherein the baffles are angled rearwardly toward the structure interface.
 6. The fish ladder of claim 5, wherein the baffles are angled at about 45 degrees relative to a bottom of the channel.
 7. The fish ladder of claim 1, further comprising at least one support leg adapted to attach to the ladder.
 8. The fish ladder of claim 7, wherein a length of the support leg is adjustable.
 9. A system for enabling fish migration comprising: a drainage structure; and a fish ladder operably couplable to the drainage structure, the fish ladder comprising: a structure interface adapted to attach to the drainage structure, the structure interface portion including a weir plate; and a ladder defining a channel for conveying water in a flow direction, the ladder including a plurality of baffles disposed across the channel generally transverse to the flow direction, the ladder operably coupled to the interface structure with a detachable hinged connection.
 10. The system of claim 9, wherein the detachable hinged connection comprises at least one hinge pin receiver on the structure interface, the at least one hinge pin receiver defining a first bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a second bore, and a hinge pin received through the first bore and the second bore.
 11. The system of claim 10, wherein the ladder is shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface.
 12. The system of claim 9, wherein the channel is defined by a pair of spaced apart substantially parallel side panels and a bottom panel extending between the side panels.
 13. The system of claim 9, wherein the baffles are angled rearwardly toward the structure interface.
 14. The system of claim 13, wherein the baffles are angled at about 45 degrees relative to a bottom of the channel.
 15. The system of claim 9, further comprising at least one support leg adapted to attach to the ladder.
 16. The system of claim 15, wherein a length of the support leg is adjustable.
 17. A fish ladder comprising: a structure interface adapted to attach to a drainage structure, the structure interface portion including a weir plate presenting a top flange and a locating structure extending upwardly from the top flange; and a ladder including a pair of spaced apart side plates and a bottom plate defining a channel for conveying water in a flow direction, the ladder including a plurality of generally planar baffles extending between the side plates generally transverse to the flow direction, the baffles being disposed such that the plane of the baffles is angled relative to the bottom plate and a top edge of each baffle is disposed closer to the structure interface than a bottom edge of the baffle, the ladder operably coupled to the interface structure with a detachable hinged connection.
 18. The fish ladder of claim 17, wherein the baffles are angled at about 45 degrees relative to the bottom plate.
 19. The fish ladder of claim 17, wherein the detachable hinged connection comprises a pair of spaced apart hinge pin receivers on the structure interface, each hinge pin receiver defining a bore, a pin receiving sleeve on the ladder, the pin receiving sleeve defining a bore, and a hinge pin received through the bores of the hinge pin receivers and the bore of the pin receiving sleeve.
 20. The fish ladder of claim 19, wherein the ladder is shiftable about the hinge pin between a first position in which the ladder extends in a horizontal orientation from the structure interface and a second sloped orientation in which the ladder slopes downwardly from the structure interface. 